1. Field of the Invention
The present invention relates to an ink set having at least two inks having specific absorbance characteristics, an image forming method, an ink jet recording method, an ink cartridge and a recording unit.
2. Related Background Art
An ink jet recording method is for forming images by applying ink droplets onto a recording medium, e.g., plain paper or dedicated glossy medium. These methods have been rapidly spreading because of reduced cost and increased printing speed. Color ink jet recording generally forms images with inks of four basic colors, three primary colors (yellow, magenta and cyan) and black.
However, some users sometimes feel that images produced with inks of these three or four colors are not satisfactory in a recorded color region as image quality of printed matter is advancing. In particular, users who demand recorded images having a quality as high as that of images produced by silver halide photography or by a laser printer with powdered toner are demanding recording systems capable of expressing a wider color reproduction range. Under these situations, a number of proposals have been made for forming images with ink colors such as red, green and blue, and further orange, violet and so on in addition to the three basic colors, i.e., three primary colors (yellow, magenta and cyan). See, e.g., WO 99/05230 and Japanese Patent Application Laid-Open No. 2000-248217.
Moreover, there are techniques focused on hue angle are proposed for recording media surface-treated to be glossy to widen a color reproduction range without deteriorating their gloss with a pigment ink (see, e.g., WO 2002/100959 and Japanese Patent Application Laid-Open No. 2004-155826).
These documents, however, simply provide a combination of inks containing coloring materials suitable for the objective hues, and are silent on relationships between coloring materials on recording media. Therefore, these techniques fail to attain a high level beyond expressing colors which satisfy the objects to some extent by, e.g., increasing an ink amount to be applied onto a recording medium or increasing a coloring material content in an ink. With a pigment used as a coloring material, in particular, it will be very difficult to keep ink reliability, with respect to ejection stability, storage stability or the like, as coloring material content increases in an ink. Therefore, images with conventional ink sets, which merely combine inks of different colors for objective image colors, may not be sufficiently satisfactory in some cases depending on hues which these ink sets try to express, compared to images produced by silver halide photography or by a laser printer with powdered toner.
An object of the present invention is to provide an ink set which can produce images with color developability undoubtedly higher than images produced by a conventional pigment ink, and closer to images produced by silver halide photography or output from a laser printer, in particular, color developability in a red color region, while keeping ink reliability.
Other objects are to provide an image forming method, ink jet recording method, ink cartridge and recording unit in which the above ink set is used.